If he had not been superhuman on clay for the last decade, tennis analysts would not be twisting themselves into knots trying to determine the hows and whys of his barren April.

Clay — unless it is colored blue — has been Nadal’s supreme medium since he manhandled Andy Roddick in the Davis Cup final in Seville, Spain, as an 18-year-old in 2004.

Ten years later, the doubts are starting to swirl like dust on a blustery day at Roland Garros.

After winning 10 titles in 2013, Nadal has won two in 2014. After losing just seven matches in 2013, he has already lost five with the heart of the season — the French Open, Wimbledon and the United States Open — yet to come.

But what truly arches eyebrows is to see Nadal searching for answers and winners on clay. So it went in the spring of 2011 when Novak Djokovic’s elastic powers briefly left Nadal looking befuddled. So it went in April in Nadal’s traditional strongholds as he lost in the Monte Carlo quarterfinals to David Ferrer and in the Barcelona quarterfinals to Nicolás Almagro, who celebrated as if he had just completed the Grand Slam instead of reaching the semifinals of an ATP World Tour 500 event.

Upsetting Nadal and the natural order can do that to a man, particularly a sensitive fellow Spaniard who had lost all 10 of their previous matches. But the upset that would really resonate would come at the French Open, which starts May 25. Nadal has won a record eight singles titles at that major tournament and has a career record that looks ever more like a typo (59-1).

Taking out Nadal at Roland Garros still ranks as the ultimate challenge. And despite the doubts and struggles of his April, Nadal clearly has ample time to recover, beginning with this week’s Masters 1000 in Madrid, where he is expected to start play Wednesday against the winner of the first-round match between Juan Monaco and Jürgen Melzer.

“If I were him, I would be far from panic,” said Paul Annacone, who coached Pete Sampras and Roger Federer. “I don’t really believe in panic anyway. But Rafa has a couple more tournaments before the French. He’s going to get plenty of matches in. He’s won the French Open 6,000 times. It doesn’t mean it’s a fait accompli, but his level of comfort should be just fine.”

That assumes Nadal is healthy, or at least healthy enough, which can be tough to glean in an era in which the leading players rarely tell the truth about what pains them. “You just never know what’s going on,” Annacone said. “Roger, last year he played and was basically hurt the whole year and doesn’t say anything to anybody publicly. But I can tell you from what we tried to do in practice and other things we had to limit. These guys can’t say anything because if they do, it becomes too big of a deal.”

If Nadal is hale and hearty, what he needs to do is resume generating consistent depth and converting on break points and stop making uncharacteristic errors and grimaces when things do not go his way.

Emilio Sánchez Vicario, the former leading player and Spanish Davis Cup captain, said in an interview Sunday that after Nadal surprised the opposition with his quick-strike, higher-risk approach in 2013, he is struggling this time to switch from hardcourts to clay. Sanchez said he also believed that Nadal’s backhand had become less reliable because of a change in footwork presumably designed to protect his fragile left knee.

“He needs to keep playing the same way because we don’t know how much he still has difficulties with the legs and where to put the weight,” Sánchez said. “But what was his best before, the defense, he has to improve it today to be less erratic. Last year he was doing it with the drive and the passion and will to become No. 1 again. Now he is No. 1 and has to find those things again to not give the opportunity to the opponent.”

Nadal’s genius has been his rare blend of tennis savvy and tennis amnesia. “It’s like what just happened doesn’t matter,” Annacone said. “All that matters is now, this second, and the next four seconds.”

But Nadal also tends to see danger at every turn, which can become, in periods of struggle, a self-fulfilling prophecy. “I don’t want to say it’s disingenuous but it’s almost like an unrealistic level of humility,” Annacone said. “Psychologically his approach helps him to be ready for every opponent and every point. That sense of urgency is so admirable, but I have to say it’s incredibly exhausting.”

Annacone does not buy the theory that Nadal is struggling to make the shift from hardcourts to clay. “What I do buy is a lot of the stuff that could be mentally or emotionally related,” he said.

The comeback from injury to No. 1 in 2013 had to be draining, just as his back problem and surprise loss to Stanislas Wawrinka in the Australian Open final this year had to be deflating as well as encouraging to the opposition. And so it might be reassuring for Nadal at this shaky stage to know that he will not have to worry this week about Djokovic, who overwhelmed him in the Miami final in March but withdrew from the Madrid event Sunday because of concerns about his right wrist.

The uncertainty about Djokovic’s health further clouds a season in which it has been difficult to see through the mists. Andy Murray, after a back operation, has not been the same player who won Wimbledon last year. Juan Martín del Potro is out of action for an extended period because of a wrist operation. Federer has been resurgent and impressive but is not yet back to vintage Federer. Djokovic just announced that his fiancée, Jelena Ristic, was expecting their first child.

“I can tell you that if I were Nicolás Almagro or Jo Tsonga or Tomas Berdych or any of these guys on the next level, I would be getting ready to try to kick the door down,” Annacone said of Paris.

For the moment, it does look slightly ajar, but when it comes to clay-court tennis, there has never been a doorman as vigilant as Nadal.

Correction:May 6, 2014

The On Tennis column on Monday, about Rafael Nadal’s recent struggles on clay, described Novak Djokovic’s wrist injury incorrectly. It is to his right wrist, not his left.

A version of this article appears in print on , on Page D6 of the New York edition with the headline: A Foothold on Clay May Be Slipping. Order Reprints | Today’s Paper | Subscribe